[gnaffle]

First of all Apple has a battery replacement program that is way, way cheaper than buying a new laptop ($129-199 for a MBP depending on the size of the laptop).

And you'll probably be able to buy aftermarket batteries just as you can with iPhones. I replaced the battery in my 3GS and it wasn't difficult at all even though the battery was glued in.

It's not like it's glued to the chassis with epoxy resin, it's designed to be replaced. iFixit didn't want to completely ruin the battery of their new laptop, so they kept it in.